This invention relates to a valve, unit, assembly and system.
In this specification geometrical terms such as upper, lower, right, left are to be understood as applying to the orientation of a valve as viewed in FIG. 1.
The same numbering is used on different drawings for the same functional parts.
Valves are widely used in industry as on-off valves for controlling the flow of liquids and gases in a pipeline, and alternatively from a pipeline and into a branch line. A valve with widespread use is a diaphragm valve in which a diaphragm is clamped in a hollow housing by their outer periphery in a manner to inhibit leakages around that periphery, and in use operates by flexure of an inwards portion of the diaphragm into and out of engagement with a valve seat. An advantage of a diaphragm valve over alternatives (such as ball valves, piston valves and butterfly valves, for example) is that it requires a lesser amount of accurate machining, and so can be cheaper to manufacturexe2x80x94for example, the piston and cylinder of a piston valve need to be very accurately machined to prevent leakages and cross-binding. Another advantage is that the opening and closing of the valve is controlled by the relative pressures at its inlet and outlet, so that large forces or torques are not required to operate the valve.
A valve xe2x80x9cunitxe2x80x9d is used when the flow into (or from) a branch pipe is to be controlled by a single diaphragm valve, or more usually when the flow into (or from) several branch pipes is independently to be controlled by several diaphragm valves.
A valve xe2x80x9csystemxe2x80x9d as described herein requires the use of at least one on-off valve. Such systems include those with a requirement for an intermittent fluid flow, including for instance a processor such as an injection mould with a requirement for intermittent coolant flow i.e. the mould needs to be cooled at least once each cycle in order to maintain the, mould temperature within an acceptable temperature range despite the mould receiving regular injections of hot plastics material (for the manufacture of plastics product). Other systems require intermittent liquid: or gas dispensing, or timed mixing.
A known diaphragm valve is shown in FIG. 1; in this known embodiment the valve is assembled from three partsxe2x80x94an upper body, part, a lower body part and a circular diaphragm clamped by its outer periphery between the upper and lower body parts. The upper and lower parts when placed face-to face form a hollow interior defined by internal surfaces within an outer (externally exposed) valve housing surface; the diaphragm is trapped by its outer perimeter between the body parts to extend across the hollow interior to form upper and lower chambers. The upper chamber (above the diaphragm) is connected to the inlet conduit by a side-porting to permit pressure equalisation to opposite sides of the diaphragm; this porting could however alternatively be an aperture through the diaphragm, the through-diaphragm aperture being the usual arrangement for most known diaphragm valves. The upper chamber is also connected by xe2x80x9cinternalxe2x80x9d porting to the valve outlet (second) conduit, this porting including a control valve.
The diaphragm is flexible, and is usually made of rubber or a suitable plastics material. It can be strengthened by a metal plate, to prevent excessive wear by the valve seat.
A typical array of diaphragm valves for independent control of flow into several branch lines is shown in FIG. 2.
A valved system for coolant flow to and from a processor such as an injection mould is disclosed in Delcroix U.S. Pat. No. 5,437,304. The Delcroix system however uses coupled mechanical valves which require a relatively large and localised operating force i.e. a force which needs to be applied as by an operating lever or handle positioned closely to the valve(s). We believe that the requirement for a large operating force makes the Delcroix system unsuitable for larger valves, and the requirement that the force be applied close to the valve(s) may not be convenient in certain applications.
From a first aspect the invention teaches a valve which includes a housing having a hollow interior within an outer housing surface, a diaphragm extending across the interior and creating a diaphragm control chamber within the interior, a valve seat against which a part of the diaphragm can seal, a first conduit leading around at least part of the valve-seat, a second conduit leading to within the valve seat, and a diaphragm control means, characterised in that the diaphragm control chamber is isolated from the first and second conduits.
From a second aspect the invention teaches a valve which includes a housing having a hollow interior within an outer housing surface, a diaphragm extending across the hollow interior to form an upper and a lower chamber, the diaphragm separating the upper chamber from the lower chamber, the lower chamber including a valve seat against which a part of the diaphragm can seal, a first conduit leading into the lower chamber and around at least part of the seat, a second conduit leading into the lower chamber and within the valve seat, a first porting leading into the upper chamber, the first porting including a control valve, characterised in that the first porting extends to an outer surface of the housing.
In an arrangement according to another aspect, the valve includes a second (prior art) porting which leads from one of the conduits and into the upper chamber, the second porting being of smaller cross section than that of that conduit. Operation of the diaphragm in this arrangement can thus in part be made dependent upon the pressure in that conduit i.e. the second porting allows, gradual pressure equalisation to opposite sides of the diaphragm such that the pressure above the diaphragm in the absence of a pilot pressure is the same as that below an outer annulus of the diaphragm or as that below a central area of the diaphragm.
When the second porting is omitted, diaphragm can be made responsive only to pressure supplied by the first porting by way of the control valve i.e. the diaphragm is driven by supplied external pressure.
An advantage of the valve according to the invention is that the first porting, can be connected to an independent control pressure, so that movement of the diaphragm against and away from the seat, and thus flexure of the diaphragm between the non-flow/conditions (between the first and second conduits) can be made dependent upon the operational position of the control valve, and in particular can be controlled by a pilot pressure in accordance with the selected on/off position of the control valve. Specifically, the pilot pressure is independent of, and can be provided by a different fluid from, that flowing in the first and second conduits. The control valve can be operated, usefully from a remote location, by any known means, including gaseous (e.g. pneumatic), liquid and electro-magnetic. Also, the valve can be bi-directional, with flow from the higher pressure conduit towards the lower pressure conduit being controlled by the valve irrespective of whether the higher pressure conduit is the first conduit or the second conduit.
Such a valve can offer the advantages of a diaphragm valve in systems which have heretofore exclusively utilised more expensive and complex mechanical valves.
In a preferred arrangement the pressure supplied to and by the pilot valve can be the higher of two available pressures. Thus the diaphragm control chamber of a valve as herein defined can be connected to a pressure selection means having a plurality of inlets connected to respective independent pressure sources, the pressure selection means automatically transmitting the highest source pressure to the chamber.
The pressure selection means can be connected to the fluid source of the valve inlet (and in certain embodiments also to a fluid source connected to its outlet), and also to an external independent pressure source, and will ensure that the pressure in the diaphragm control chamber always exceeds the pressure at the inlet and outlet, so that the position of the valve can be maintained open or closed as desired, regardless of changes in the source pressure(s).
The diaphragm control means can be a pilot valve within the valve housing, or one remote from the valve housing and connected thereto by a pressure line.
From a third aspect the invention teaches a valve unit, each unit including a valve having a housing which includes outer surfaces and within which is an upper and a lower chamber, a diaphragm separating the upper and the lower chamber, the lower chamber including a valve seat against which a part of the diaphragm can seal, a first conduit with first and second ends and with the second end leading into the lower chamber and around at least part of the seat, a second conduit leading into the lower chamber and within the valve seat, a first porting leading into the upper chamber, the first porting including a control valve, characterised in that a first end of each first conduit is joined to a flow-passageway at a position part-way along the passageway, and in that the ends of the passageway are formed to interconnect with a passageway of another valve unit so as to permit a modular valve assembly.
As with the prior art arrangement, the valve unit can include a second porting leading from the first conduit into the upper chamber, the second porting being of smaller cross-section than the first conduit.
The individual passageways can be connected to form a pipeline, usually open-ended but alternatively with the passageway of one valve unit being blanked off so that the pipeline becomes closed-ended at that valve unit; the major medium flow will occur along the pipeline and continue through the passageways towards another (downstream) valve. The valves can be pilot operated, individually and perhaps in sequence, to allow each respective diaphragm to lift from its seat whenever medium needs to be tapped off from the pipeline i.e. specifically from its respective passageway, and fed to and through the second conduit and out of that valve; if the second conduit is connected to a second pipeline the valve can achieve controlled medium transfer between the first and second pipelines. Alternatively, it can be arranged that the medium flows from the second conduit through the valve and into the passageway and first pipeline, for instance for pilot-controlled mixing or dosing applications.
An advantage of such a unit when the diaphragm housing also embraces a through-passageway which can form part of a pipeline i.e. when one or more units are mounted in-line between pipe sections, is a reduced number of leak, points i.e. as compared with fitting a known diaphragm valve such as that of FIG. 1.
The valves can however alternatively be spaced apart individually along a pipe, with their respective ends joined to intermediate pipe sections.
From a fourth aspect the invention teaches a flow control system for a processor which includes a processor inlet valve and a processor outlet valve characterised in that at least one of the valves is a valve as described herein. Preferably, there is a processor dump valve connected upstream of the outlet valve and at least the processor outlet valve and the dump valve are controlled by a (common or independent) pilot valve whereby the dump valve can be in the closed condition when the inlet and outlet valves are in the open condition and whereby the dump valve can be in the open condition when the inlet and outlet valves are in the closed condition.
Preferably, the processor inlet valve is also controlled by a pilot valve. Preferably also, a single pilot valve controls at least one, and usefully all, of the processor valves. The processor valves can be operated sequentially or substantially simultaneously by the pilot valve.
Desirably, the pilot valve(s) is(are) remote from each respective valve.
An advantage of this system when connected to a processor such as an injection mould (to control the flow of coolant to and from the processor) is that when the mould is to be changed and the inlet and outlet valves are closed, the dump valve can be opened so as to allow sufficient of the flow medium (such as liquid coolant) trapped in the processor to be taken off in controlled fashion whereby to allow the pressure of the trapped coolant to drop to ambient. Thus the xe2x80x9cback-pressurexe2x80x9d trapped in the mould when the outlet valve was closed can be reduced, so that when the mould is subsequently disconnected from the inlet/outlet valves the coolant does not eject forcibly from the processor. The pilot valves can be controlled from adjacent the position from which the mould is to be disconnected, allowing both operations to be supervised and/or effected by one operator, even though the dumped coolant can be received and/or stored at a different position e.g. to the rear of the processor.